In a pinch

Officials in Toronto are not happy about the spread of the rusty crayfish (Orconectes rusticus) through the rivers and creeks of the region, according to this article from The Globe and Mail. The province of Ontario already has its share of native crayfish species, but none of them seem to have the attitude problem of the slightly larger rusty crustaceans. They are more aggressive than their native cousins, will out-compete them in the grab for food, and tend to have voracious appetites. They're also more likely to attack your toes than to run away if you disturb them. Rusty crayfish are considered native to the U.S., including some of the Great Lakes states, but have greatly expanded their range over the past several decades.